In the renin-angiotensin system (RAS) the biologically active angiotensin II (Ang II) is generated by a two-step mechanism. The highly specific enzyme renin cleaves angiotensinogen to angiotensin I (Ang I), which is then further processed to Ang II by the less specific angiotensin-converting enzyme (ACE). Ang II is known to work on at least two receptor subtypes called AT1 and AT2. Whereas AT1 seems to transmit most of the known functions of Ang II, the role of AT2 is still unknown.
Modulation of the RAS represents a major advance in the treatment of cardiovascular diseases. ACE inhibitors and AT1 blockers have been accepted to treat hypertension (Waeber B. et al., “The renin-angiotensin system: role in experimental and human hypertension”, in Birkenhager W. H., Reid J. L. (eds): Hypertension, Amsterdam, Elsevier Science Publishing Co, 1986, 489-519; Weber M. A., Am. J. Hypertens., 1992, 5, 247S). In addition, ACE inhibitors are used for renal protection (Rosenberg M. E. et al., Kidney International, 1994, 45, 403; Breyer J. A. et al., Kidney International, 1994, 45, S156), in the prevention of congestive heart failure (Vaughan D. E. et al., Cardiovasc. Res., 1994, 28, 159; Fouad-Tarazi F. et al., Am. J. Med., 1988, 84 (Suppl. 3A), 83) and myocardial infarction (Pfeffer M. A. et al., N. Engl. J. Med., 1992, 327, 669).
The rationale to develop renin inhibitors is the specificity of renin (Kleinert H. D., Cardiovasc. Drugs, 1995, 9, 645). The only substrate known for renin is angiotensinogen, which can only be processed (under physiological conditions) by renin. In contrast, ACE can also cleave bradykinin besides Ang I and can be by-passed by chymase, a serine protease (Husain A., J. Hypertens., 1993, 11, 1155). In patients, inhibition of ACE thus leads to bradykinin accumulation causing cough (5-20%) and potentially life-threatening angioneurotic edema (0.1-0.2%) (Israili Z. H. et al., Annals of Internal Medicine, 1992, 117, 234). Chymase is not inhibited by ACE inhibitors. Therefore, the formation of Ang II is still possible in patients treated with ACE inhibitors. Blockade of the AT1 receptor (e.g. by losartan) on the other hand overexposes other AT-receptor subtypes (e.g. AT2) to Ang II, whose concentration is significantly increased by the blockade of AT1 receptors. In summary, renin inhibitors are expected to demonstrate a different pharmaceutical profile than ACE inhibitors and AT1 blockers with regard to efficacy in blocking the RAS and in safety aspects.
The present invention relates to the identification of renin inhibitors of a non-peptidic nature and of low molecular weight. Specifically, orally active renin inhibitors are described which are of long duration of action and active in indications beyond blood pressure regulation where the tissular renin-chymase system may be activated leading to pathophysiologically altered local functions such as renal, cardiac and vascular remodeling, atherosclerosis, and possibly restenosis.
The compounds described in this invention represent a novel structural class of renin inhibitors.